Prostate brachytherapy is an increasingly popular treatment for clinically localized prostate cancer.In properly selected patients, it is highly effective with biochemical (PSA) disease free survival rates of 80-87% at 5-10 years.However, the technique is currently limited by the inability to localize the cancer within the prostate. The multifocal nature of prostate cancer is well established. Because of the inability to know where within the prostate the cancer is located, radiation must be delivered throughout the gland. Although this blind approach leads to good results, it is clear that there are regions of the prostate and surrounding tissue that are overexposed to radiation while others are underexposed relative to their true need based on their tumor burden and their proximity to the tumor areas.Feleppa et al. at Riverside Research Institute (New York, NY), a non-profit ultrasound research center, have developed an ultrasound-based technique to identify cancer-containing areas within the prostate. This technique uses current ultrasound equipment already in use for prostate brachytherapy guidance. By extracting and processing the radiofrequency signal obtained from the ultrasound transducer in ways not done to create the standard B-mode ultrasound image, areas of cancer can be identified and displayed overlying the standard B-mode ultrasound image.In this study, we propose to obtain these ultrasound-based cancer-specific images of the prostate prior to the brachytherapy and use them to direct the dosimetry planning.The primary goal of this study is to demonstrate that this imaging modality can be incorporated into the treatment planning process for brachytherapy. Furthermore, we wish to demonstrate the improved dosimetry of the cancer-identified regions while maintaining the urethral dose guidelines noted above. We also wish to compare the differences in dose to the other adjacent normal structures (anterior rectum and right and left neurovascular bundles). Additionally, we seek to demonstrate, at a minimum, no increased toxicity with this approach and similar disease control rates. Of course, ultimately the goal will be to demonstrate a superior therapeutic ratio with this technique.